1. Field of the Invention
The present invention relates to an ophthalmic measuring apparatus for examining the crystalline lens of the eye, and more particularly to improvements in the alignment system of an ophthalmic measuring apparatus for examining the crystalline lens by projecting a laser beam on the eyeball of the eye, guiding scattered laser light scattered by the crystalline lens through a light-receiving optical system to a photoelectric transducer and determining the condition of the crystalline lens on the basis of the output signals of the photoelectric transducer.
2. Description of the Related Art
A known ophthalmic measuring apparatus for examining the crystalline lens of the eye projects a laser beam on the crystalline lens, and detects scattered laser light scattered by molecules contained in the crystalline lens to examine the crystalline lens for cataract.
When aligning the ophthalmic measuring apparatus with a desired region on the crystalline lens, the examiner observes the crystalline lens and the laser beam through an observation optical system to determine the position of the ophthalmic measuring apparatus relative to the crystalline lens, and determines subjectively the position of the ophthalmic measuring apparatus relative to the desired region on the crystalline lens. The ophthalmic measuring apparatus makes a note of position data on the approximate relative position of the ophthalmic measuring apparatus on a memo sheet to store the position data for determining the position of the ophthalmic measuring apparatus relative to the same desired region in the next examination.
However, since the position data is determined subjectively by the examiner through the observation of the position of the laser beam relative to the crystalline lens of the eye, different position data are obtained by different examiners for the same desired region. Accordingly, the repeatability of the examination of the same desired region is low and, consequently, accurate age-based examination of the same desired region is impossible.
When aligning the ophthalmic measuring apparatus of this type with a measuring region, the positional relation between an image of the front of the eye and the laser beam is observed through the observation optical system. Therefore, a large magnification is used to achieve accurate alignment and minute observation of the measuring region and its vicinity.
However, when a large magnification is used, the rough observation of the eye is impossible and it is difficult to find the positional relation between the ophthalmic measuring apparatus and the eye. Consequently, the aligning operation takes a long time, exerting load on both the examiner and the subject.